In a photovoltaic power generation system from which high output is required, typically strings composed of a large number of series-connected modules are connected in parallel. For efficient power generation, Maximum Power Peak Tracking (MPPT) control has been increasingly applied by a power conditioner (PCS) or the like. Consider detecting a string with an abnormal module in the case where power generation output data is measured only in the string-basis.
A method has been proposed for detecting abnormal modules only from data on past output performance without the use of a special abnormality detection circuit or a solar radiation sensor. This method groups power generation systems beforehand according to similarity of geographic proximity and/or installation conditions, and compares the amounts of power generation within a group with each other to find a system with relatively low generation output as an abnormality.
It is conceivable to apply this existing technique to compare power generation output data for individual strings in a photovoltaic power generation system to detect a string including an abnormal module. The technique, however, is not intended for a photovoltaic power generation system with strings controlled at the same voltage by a power conditioner according to Maximum Power Peak Tracking (MPPT), and thus it can make an erroneous determination as a result of output power comparison.
When power generation output data is measured only in the string basis in a photovoltaic power generation system, it will be more difficult to identify a string including an abnormal module as the level of serialization increases. Also, when one PCS performs MPPT control on multiple arrays of parallel-connected strings, the difference in output power becomes smaller at a higher level of parallelism, leading to an error of abnormality determination.